[fdo-users] RE: RE: Defining SpatialContext - how and when?
Gavin Cramer
gavin.cramer at autodesk.com
Mon Jul 9 11:36:11 EDT 2007
Ah, yes, this was with SQL Server. Sorry about that.
I believe that you have come across a defect in SQL Server Provider 3.1.
Actually, it could be two defects at once (a spatial indexing
limitation, and a wrong error message). They were fixed in 3.2.x (for
the 2008 versions of Map and MapGuide). There is a workaround.
One problem is that the wrong message is issued (it's off by one entry
if you peek at the catalogue). The correct message is:
"Geometric value is outside of spatial index extents"
This could come from two sources, one of which is the second defect:
1. You might really have some geometry value that is outside of the
extents.
2. You might have hit a problem in the FDO provider with spatial
indexing using large extents and small XY tolerance. The error message
would be either what you have seen, or a generic bad parameter
exception. There is a workaround.
Looking at your extents and tolerance, you might encounter issue #2
eventually, even if it is not the cause of your current problem. The
basically, the spatial index internally has a 32-bit precision, which is
plenty for a real-world data in GIS with a reasonably well-chosen
extent. However, the internal check was incorrect, and some
calculations can go wrong if you specify a too-small XY tolerance. The
spatial index's precision is the main use for the spatial context's XY
tolerance in SQL Server Provider 3.1.
The calculation of the smallest usable tolerance is simple: "largest
extent" / (2^31 - 1).
Yes, that's 31, not 32, in that calculation. That's just being
defensive to avoid boundary cases. Anyway, your extent is 7000000, so
your smallest tolerance should be about 0.00326.
Gavin
-----Original Message-----
From: fdo-users-bounces at lists.osgeo.org
[mailto:fdo-users-bounces at lists.osgeo.org] On Behalf Of Maksim Sestic
Sent: Monday, July 09, 2007 5:50 AM
To: fdo-users at lists.osgeo.org
Subject: [fdo-users] RE: RE: Defining SpatialContext - how and when?
Huh, funny thing but "Autodesk.SqlServer.3.1" provider connection
capabilities on SpatialContext report following:
- SupportsCSysWKTFromCSysName: False
- SupportsMultipleSpatialContexts: True
I guess I still need to set spatial context WKT by hand and this setting
shouldn't affect geometries that will get inserted during next stage.
Anyway, I tried three different approaches and all of them failed,
raising
"Error
creating spatial context (null) (SRID=486518961), the WKT provided does
not
match the catalog." exception:
1) create DataStore, then insert new SpatialContext (with WKT string
defined
by hand) and associate schema class geometric properties with newly
created
CS (using SpatialContextAssociation).
2) create DataStore, then insert new SpatialContext (without WKT string)
and
associate schema class geometric properties with newly created CS (using
SpatialContextAssociation).
3) create DataStore, then delete "Default" spatial context and create a
new
"Default" one with different precision and envelope (but without WKT
string,
as in it's original settings). Geometric properties, when instantiated
within schema class, are set to "Default" CS by default so I don't need
to
manually set them.
The other solution is to convert any MGI coordinate to WGS84 and let
them
into the datastore using "Default" CS, but this is actually not a good
one
since certain coordinate conversions are "one way only" when talking
about
precision. My datastore is supposed to keep GPS-measured coordinates
precise
to a few millimeters, while coordinate conversion roundtrip (MGI ->
WGS84 ->
MGI) involves overall imprecision measured in meters :-)
Regards,
Maksim Sestic
Gavin Cramer wrote:
>
> Ah, yes, the WKT...
>
> WKT only needs to be manually set (using
> FdoICreateSpatialContext::SetCoordinateSystemWkt() for FDO providers
that
> cannot generate WKT. This is the case for most providers (because
their
> underlying datastores don't have native coordinate system support).
>
> For those that do natively support coordinate systems (like Oracle),
the
> provider may also verify that the coordinate system name and WKT are
in
> the datastore's catalogue. It's generally just a blind string
comparison,
> so minor variations may cause a failure in WKT. To avoid this, just
omit
> setting the WKT attribute.
>
> There is an FDO capability to let you know whether WKT generation is
> supported: FdoIConnectionCapabilities::
SupportsCSysWKTFromCSysName().
>
> By the way, while your code for creating a LineString will work, the
> FdoIDirectPosition type is not yet a pooled object, and will result in
a
> lot of heap activity. I recommend looking at the other constructors
that
> are more efficient if you plan to use a lot of features. For example,
> there is one that takes an array of ordinates. There are accessors
that
> tend to be much faster as well. For example, GetItemByMembers() is
the
> fastest one that does all the ordinate reading for you, and
GetOrdinates()
> is the fastest if you want a raw ordinate array.
>
> Gavin
>
>
>
>
> -----Original Message-----
> From: fdo-users-bounces at lists.osgeo.org on behalf of Maksim Sestic
> Sent: Sat 07-Jul-07 10:28 AM
> To: fdo-users at lists.osgeo.org
> Cc:
> Subject: [fdo-users] RE: Defining SpatialContext - how and when?
>
>
> Dear Gavin,
>
> Thanks for the tip. It's still bugging me. Here's what I'm doing:
>
> 1) create new DataStore named "GIS"
>
> 2) create SpatialContext named "MGI" using following parameters:
> - Name: MGI
> - Description: MGI
> - Coordinate System: MGI / Balkans zone 6
> - Coordinate System WKT: PROJCS["MGI / Balkans zone
>
6",GEOGCS["MGI",DATUM["Militar_Geographische_Institute",SPHEROID["Bessel
>
1841",6377397.155,299.1528128]],PRIMEM["Greenwich",0.000000],UNIT["Decim
al
>
Degree",0.01745329251994330]],PROJECTION["Transverse_Mercator"],PARAMETE
R["Centr
>
al_Meridian",18],PARAMETER["Scale_Factor",0.9999],PARAMETER["False_Easti
ng",6500
>
000.000000],PARAMETER["False_Northing",0.000000],UNIT["Meter",1.00000000
0000]]
> - XY Tolerance: 0.0001
> - Z Tolerance: 0.0001
> - Extents Type: SpatialContextExtentType_Static
> - Extents range from 0,0 to 7000000,7000000
>
> 3) create schema "TESTSCHEMA" containing one class "TESTCLASS" with
> GeometryValue defined as:
> geomProperty.GeometryTypes = 7
> geomProperty.SpatialContextAssociation = "MGI"
>
> -------------
>
> Still, when I try to issue an Insert on some geometry ti throws "Error
> creating spatial context (null) (SRID=486518961), the WKT provided
does
> not
> match the catalog." again.
>
> Here's the geometry definition (sitting within specified spatial
context
> extents):
>
> Dim insertCommand As IInsert =
>
CType(m_Transaction.Connection.CreateCommand(CommandType.CommandType_Ins
ert),
> IInsert)
> insertCommand.SetFeatureClassName("TESTSCHEMA:TESTCLASS")
>
> Dim factory As AgfGeometryFactory = New AgfGeometryFactory()
> Dim pcollection As DirectPositionCollection = New
> DirectPositionCollection()
> pcollection.Add(factory.CreatePositionXY(6500001, 4950001))
> pcollection.Add(factory.CreatePositionXY(6534554.445, 4958445.342))
>
> Dim line As ILineString = factory.CreateLineString(pcollection)
> Dim geometryValue As GeometryValue = New
> GeometryValue(factory.GetAgf(line))
> insertCommand.PropertyValues.Add(New PropertyValue("geometry",
> geometryValue))
> insertCommand.Execute()
>
> ---------------------------
>
> Regards,
> Maksim Sestic
>
>
>
>
> Gavin Cramer wrote:
>>
>> Hello, Maksim. The "active" spatial context is a bit of a stale
idea,
>> and might become deprecated. Any provider that currently cares about
it
>> actually sets it internally, based on the relevant geometric
property's
>> spatial context association.
>>
>> The association can be set when creating a schema definition via
>> FdoGeometricPropertyDefinition:: SetSpatialContextAssociation().
>>
>> Gavin
>>
>>
>> -----Original Message-----
>> From: fdo-users-bounces at lists.osgeo.org
>> [mailto:fdo-users-bounces at lists.osgeo.org] On Behalf Of Maksim Sestic
>> Sent: Saturday, July 07, 2007 8:50 AM
>> To: fdo-users at lists.osgeo.org
>> Subject: [fdo-users] Defining SpatialContext - how and when?
>>
>>
>> Autodesk Map 3D 2007 / MS SQL Server 2005
>>
>> I have problems inserting a new GeometryValue due to the "Default"
>> SpatialContext settings. "Default" SpatialContext has an envelope
>> (extents)
>> ranging from -2000000,-2000000 to 2000000,2000000, while my geometry
>> lies
>> way beyond default settings. Due to that fact, I keep receiving
>> following
>> error: "Error creating spatial context (null) (SRID=486518961), the
WKT
>> provided does not match the catalog."
>>
>> I tried to update Extents value on "Default" spatial context using
>> CreateSpatialContext command but it's not working (well, at least
>> nothing
>> changes in dbo.f_spatialcontextgroup table). Then I resorted to
creating
>> a
>> new SC.
>>
>> Now, I managed to create a new SpatialContext (named "MGI") with
>> associated
>> WKB string, proper extents settings, etc. Alas, I can not activate it
>> :-)
>> ActivateSpatialContext command does not affect present spatial
contexts
>> within DataStore - ISpatialContextReader always returns IsActive =
False
>> for
>> every SC present.
>>
>> I think I'm doing something wrong here, just can't figure out exactly
>> what... :-) At what moment do I need to create custom SpatialContext
>> (before
>> or after creating feature schema?), and how do I apply newly
established
>> SC
>> on present schema? How do I "force" my newly inserted geometric
values
>> "conformant" to present SC?
>>
>> Regards,
>> Maksim Sestic
>>
>>
>> --
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>> 18162.html#a11478212
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